installer.md

Installer Implementation

An installer controller is responsible to provide the installation and uninstallation scripts for k8s dependencies, prerequisites and components on each BYOHost. We provide a default installer (K8sInstallerConfig) to install the supported upstream k8s. If someone wants to implement their own installer controller then they need to follow the following contract:

Data Types

1. Must create a CustomResourceDefinition InstallerConfigTemplate for your installerConfig (eg. K8sInstallerConfigTemplate)
2. Must create a CustomResourceDefinition InstallerConfig (eg. K8sInstallerConfig)
3. Must be namespace-scoped
4. Must have the standard Kubernetes type metadata and object metadata
5. Must have a status field with the following:
   1. Required fields:
      1. Ready (boolean): indicates the installation secret has been generated and is ready
      2. InstallationSecret (ObjectReference): reference to installation secret
   2. Optional fields:
      1. failureReason (string): indicates there is a fatal problem reconciling the installer configuration; meant to be suitable for programmatic interpretation
      2. failureMessage (string): indicates there is a fatal problem reconciling the installer configuration; meant to be a more descriptive value than failureReason

Reconcile flow

• If the resource does not have a ByoMachine owner, exit the reconciliation
• If the Cluster to which this resource belongs cannot be found, exit the reconciliation
• If ByoMachine.status.condition.ByoHostReady reason is not equal to InstallationSecretNotAvailableReason, exit the reconciliation
• If status.ready is true, exit the reconciliation
• Deterministically generate the name for the installation secret
• Try to retrieve the Secret with the name from the previous step
  • If it does not exist, generate installation/uninstallation data using ByoMachine.status.hostinfo details and create the Secret with the following data:
    • install (string): contains installation bash script
    • uninstall (string): contains uninstallation bash script
  • Variables: need to keep these variables in the scripts to parse by the byoh agent.
    • {{.BundleDownloadPath}}: path on host where bundle will be downloaded by byoh agent
• Set status.installationSecret to the generated secret object reference
• Set status.ready = true
• Patch the resource to persist changes

Installer Template

ByoMachine refers to an installer template ByoMachineTemplate.spec.template.spec.installerRef. So, ByoMachine controller will create the Installer CR using the InstallerTemplate for each ByoMachine.